This invention is directed to a structural arrangement for reactor cores. In particular, the invention is directed to a core arrangement for stabilizing saturated reactors and for simulating a linear reactor. The invention is not directed to a saturable reactor. Saturable reactor cores must be designed to account for a bias current winding. The present invention operates off AC line without bias current.
Slotted core formations for reactors are well known in the art. For example, see U.S. Pat. Nos. 2,907,957, 3,150,340 and 1,606,777. In general, the number, size and location of slots in a magnetic core is determined by the intended application for the core. In U.S. Pat. No. 2,907,957, there is described a saturable magnetic core for use in an electrically variable delay line. The core must have a substantially linear inductance versus bias current curve. Signal loss should be minimized. The magnetic core is provided with a circumferential notched portion which supports two oppositely poled signal windings. The purpose of the notch is to confine the signal field to a restricted portion of the core to reduce losses in the energy field due to the core itself. The bias current winding is wrapped around a remaining portion of the core.
Restriction of the signal field can be enhanced by forming a narrow slot at each end of the notch. These narrow slots enable a substantially linear inductance versus bias current curve to be attained. The inductance of the reactor is varied by varying the bias current. The bias current determines the incremental permeability of the magnetic core and, therefore, the reactance of the core to relatively low amplitude alternating current signals.
There are many instances where a reactor must operate in a reasonably stable manner although in a magnetically saturated condition. For example, a reactor operating off an AC line without bias current may be driven deep into saturation under relatively high alternating voltage and current conditions. Minor fluctuations in the applied alternating voltage may result in current swings 20 times greater. This instability of the saturated reactor imposes a severe burden on the power supply. In addition, it results in objectionable deviation from impedance and power factor balance conditions.
Heretofore, a saturated reactor operating off AC line could be stabilized by connecting a linear choke in series with the reactor. The choke would be rated at the same current as the saturated reactor and would produce a voltage drop sufficient to introduce the required degree of stability in the reactor. Where the energy levels under consideration were as high as hundreds or even thousands of KVA, the design of an effective linear choke became quite involved and expensive.
A technique for simulating a series choke for a saturated reactor is disclosed in U.S. Pat. No. 3,295,050 assigned to the assignee herein. The magnetic core was surrounded by a bonded, powdered iron structure having a generally linear magnetic characteristic. A common winding surrounded the entire assembly. The powdered iron was arranged in a ring and was dimensioned to introduce the necessary degree of electrical stability to the assembly.
The bonded rings disclosed in U.S. Pat. No. 3,295,050 performed satisfactorily in stabilizing the saturated reactor. The assembly, however, suffered from certain objectionable features such as excess heating due to losses in the bonded ring, marked magnetic saturation in the ring, and unavoidably high labor costs in assembling the core and bonded ring to form the final reactor.
To date, there is a compelling need for a magnetic core structure for a saturated reactor operable off AC line without objectionable instability. Such a core structure should be relatively simple to assemble and should minimize the costs of manufacture. The core should also exhibit mechanical strength and integrity.